In the 1990s, energy saving technologies in the field of railway vehicles had not been wrestled with actively because of a cost-benefit point of view. In the 2000s, they had been interested in decreasing greenhouse gas as a countermeasure against global warming. In the year of 2006, the revised Rationalization in Energy Use Law obliged major railway companies which owned more than three hundred vehicles to report on the plans and actual results of their measures for the reduction of energy consumption, with the result that further countermeasures are sought after. This report introduces the recent studies and developments of energy saving technologies in the field of railway vehicles.

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Various natural disasters have occurred in Japan due to geological and meteorological conditions, causing significant human loss and economic damage. Disaster prevention technology for railways has been developed through experience and has contributed to mitigating damage. Since the 2011 off the Pacific coast of Tohoku Earthquake, however, the paradigm of disaster prevention has shifted. Japanese Government disaster prevention now focuses on mitigating the impact of and resilience against large-scale disasters caused by forces larger than those considered up until now. This paper introduces the results of recent research into disaster prevention technology, and describes research plans for mitigating the impact of and resilience against large-scale disasters.

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The Railway Technical Research Institute opened the Center for Railway Earthquake Engineering Research on April 1, 2014 amid increasing concern about the risk of seismic disasters caused in particular by massive earthquakes. Violent earthquake disasters are becoming more common and more complex. In order to achieve safer railway systems able to cope with these conditions, the center was established as a unique "base" for railway-seismic technology in Japan. The center also integrates RTRI's research resources on quake-motion, seismic design and countermeasure, and early warning. This report introduces the role of CREER and recent research into earthquake-related technology.

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In recent railway traction systems, squirrel-cage induction motors are commonly used as traction motors. They are usually driven by a voltage source inverter with a single-pulse waveform at high speed. The single-pulse waveform contains lower harmonics that induce additional loss in the motors. Therefore, this paper studies the optimization of three-pulse and five-pulse waveforms which could replace single-pulse waveforms to reduce additional loss. This paper proposes three-pulse and five-pulse waveforms that are optimized to minimize additional loss while maximizing fundamental components. The effectiveness of the proposed waveforms was verified through finite element analyses. The results showed that the proposed waveforms are able to improve motor efficiency by about one percent compared with single-pulse waveforms.

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The adhesion coefficient between rail and wheel of the railway vehicle is reduced under rainy weather, so it is difficult to obtain high braking performance. In general, the braking performance of the train is evaluated to be based on the stopping distances and the deceleration which is obtained by calculating the rotational velocity of the wheel. However, braking performance degradation is caused by the complex combination of the bad condition of the adhesion coefficient between rail and wheel, the friction coefficient of composite braking materials and the wheel slip control. In order to investigate the factor of the degradation of the braking performance in the high speed train or the shortening of the braking distance, it is desired to measure the variation of the braking force at each bogie. We have developed an evaluation method of measuring the braking force of the actual vehicle with the force acting on the single-link type traction device. In this paper, the results of a running test by means of this evaluation method of the braking performance using bogie traction force are reported.

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This paper presents a method for reducing flexural vibrations in a railway vehicle carbody by supporting under-floor equipment using high-damping elastic mounts. This is a kind of dynamic vibration absorber utilizing under-floor equipment as a mass element which has been introduced based on the inspiration of the damping effect of passengers. A series of excitation tests were conducted in the rolling stock testing plant using a Shinkansen type test vehicle by applying the proposed method. As a result of the tests, good vibration reduction performance, including multi-modal vibration reduction and vibration isolation from the equipment, was observed.

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This paper proposes a method for evaluating train running safety in strong wind conditions using the probabilities of strong wind occurrence according to wind direction. The Weibull coefficients c_d and k_d for 16 wind directions were calculated on the basis of data from 10-min maximum instantaneous wind velocities for each wind direction at 772 Automated Meteorological Data Acquisition System (AMeDAS) stations. Probabilities P_x of the occurrence of strong winds exceeding the critical wind speeds for overturning were estimated for a train in a virtual railway section by using c_d and k_d calculated on the basis of the wind data observed at a windy AMeDAS station. P_x values were found to vary from 6.2×10^-6 to 8.6×10^-5 depending on the angle between the traveling direction of the train and each wind direction. The values of P_x ranged from 1.4% to 20% of the P_y values, which were calculated out of consideration of strong wind occurrence according to wind direction.

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Groundwater levels in embankments often rise due to heavy rainfall, which can occasionally cause embankments to collapse. In order to decrease the ground water level, it is important to take countermeasures to drain the water from areas in embankments which could weaken in heavy rain. The drain pipe method for embankments has been adopted widely by Japanese railways as a water draining method. However, installation specifications for drain pipes have not yet been established, and the finer details of construction work currently depend on experience. This study therefore set out to evaluate the effect of drain pipes quantitatively, with a view to proposing a set of installation specifications for drain pipes in embankments, based on the evaluation and considering the height of the embankment, external permeance, inter alia.

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Previous studies have reported that topographical and geological conditions influence shallow landslides. However, identifying unstable slopes based on these conditions needs professional knowledge and detailed surveys. This report statistically examines topographical and geological data in order to extract topographical and geological conditions which are useful for identifying unstable slopes from those reported in previous studies. Based on the results, a simple procedure is proposed for identifying unstable slopes.

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In this paper, a new vibration control device realizing negative stiffness in a passive manner is proposed in order to reduce the absolute response of structures under strong seismic motions. The developed device consists of a sliding plate with a PTFE portion, and they are vertically pressurized by coil springs. The shape of the sliding plate is convex, by which the control force is negatively proportional to the deformation. The prototype of the proposed device was assembled, and its performance was investigated through both sinusoidal and hybrid loading tests. It was confirmed that the proposed device reduced the maximum acceleration of the structure significantly without any significant increase in absolute displacement.

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Improvements were made to the algorithms used for earthquake early warning, followed by tests to validate their performance for actual use. The upgraded algorithms are capable of producing more accurate and timely estimations of seismic parameters, compared with current algorithms. This new technique contributes to raising train operating safety during earthquakes. Another enhanced algorithm was devised for seismographs installed along railway lines, which makes them capable of discriminating between earthquake motion and train-induced vibrations. These improvements to the seismographs are expected to increase the reliability of earthquake early warning.

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Pile bent structures have no underground beam, so the distribution of bending moments between the pile and pier is continuous. It is therefore considered that the dynamic response characteristics of the pile bent are complexly affected by the displacement of the ground and inertial forces, but this inertial and kinematic interaction is unclear. In this paper, the inertial and kinematic interaction acting on the pile bent structures is studied by nonlinear time-history dynamic analysis. As a result, it is revealed that the moment due to the inertial force is dominant on the pier and the pile which is located at a small depth, and the displacement of the ground has an influence not only on the moment at the pier but also that at the pile.

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